The disclosure relates to aerospace coatings for metallic substrates. More particularly, the disclosure relates to application of coatings to parts having cooling holes.
A variety of metallic parts used in gas turbine engines have fine cooling holes. Typical cooled parts comprise nickel-based or cobalt-based superalloys. Typical parts are formed by casting and they include: combustor panels; blades, vanes, or other airfoil members; blade outer airseals (BOAS); and the like. A typical such component is formed by a combination of casting and machining. Cooling holes may be formed post-casting (e.g., via mechanical machining, electro-discharge machining, laser machining, or the like) or may be cast in place such as via refractory metal cores.
The components often comprise a thermal barrier coating (TBC) system comprising one or more ceramic layers. One or more bondcoat or other layers may intervene between the ceramic layer(s) and the substrate. When the holes preexist coating application, the possibility exists of the coating plugging the holes (fully or partially). Even if the coating does not plug the holes, coating may deposit along the interior surfaces of the holes. Coated surfaces may reduce heat transfer along the holes.
Exemplary combustor panels and coatings are disclosed in U.S. Patent Application Publication No. 2012/0167573A1, Jul. 5, 2012, and U.S. Pat. No. 7,093,439, Aug. 22, 2006, the disclosures of which are incorporated by reference herein in their entireties as if set forth at length.